Web Accessibility Made Easy

U.S. Government Website Accessibility Guidelines

Introduction

This document was assembled by and with the help of NASA webmasters to assist NASA and other Federal webmasters in the goal of making all Government websites accessible to persons with disabilities. The information below represents source material and the actual guidelines with descriptions of intent and suggested methods of compliance. In addition to the guidelines, information on specific assistive technology developments and how they are used is found here on the Assistive Technology page.

A text equivalent for every non-text element shall be provided (e.g., via <alt>, <longdesc>, or in element content).

The <alt> text tag provides a title or descriptive phrase about the image it accompanies. This is essential for users of reader software who are vision impaired and it is valuable for users of graphical browsers who have "load images" turned off. It is also useful for users of text-only WWW tools like Lynx. The <longdesc> tag can be essential when an image conveys important information such as what about the image represents a discovery if the image is a science result image.

This states that any dynamic changes which occur based on multimedia content (either in a <frame>, <img>, <object>, or <script>) must also update the "alt" element when it changes.

(c)

Web page design

Web pages shall be designed so that all information conveyed with color is also available without color, for example from context or markup. Good primer on Color BlindnessLink used with author's permission.

Thirty percent of all males suffer from some form of color deficiency rendering colors as grays or spreading one color across several others. Choose text and background colors to provide maximum contrast. Contrast is also very important for individuals who can see but have reduced vision. Good design also refers to the ability of reader software to properly parse a page correctly left to right and up to down.

Frames present unique obstacles to users of reader software. A frame-based page should always include an alternative layout (text only) inside a <noframe> element. Also, with the <title>, <name> and <longdesc> tags, frames can be made more navigable for reader software.

(j)

Web page design

Pages shall be designed to avoid causing the screen to flicker with a frequency greater than 2 Hz and lower than 55 Hz.

Flicker and continuous motion (as from applets or javascripts or from refreshes) can cause seizures in individuals with photosensitive epilepsy. Content developers should refrain from an overuse of time-sequenced elements. If used, the timing should be longer than half-a-second.

(k)

Organization & equivalent alternatives

A text-only page, with equivalent information or functionality, shall be provided to make a web site comply with the provisions of this part, when compliance cannot be accomplished in any other way. The content of the text-only page shall be updated whenever the primary page changes.

Content developers should only resort to alternative pages when other solutions fail. An out-of-date page may be as frustrating as one that is inaccessible since, in both cases, the information presented on the original page is unavailable. &nbspBefore resorting to an alternative page, reconsider the design of the original page

The easiest method to provide this accessible alternative is to write HTML code which includes the <noscript> tag. Other options include ensuring that dynamic content and refreshes can be made or are accessible.

Objects and data which require plug-in applications can be presented in HTML code in a nested manner such that, if the user's browser can't display the topmost data type, it will attempt to display equivalent data type in the object specification. This is more complicated HTML code to create and requires several data types to be resident on the server, but it is a more complete method of inclusion which favors neither advanced nor dated browser technology.

(n)

Forms

When electronic forms are designed to be completed on-line, the form shall allow people using assistive technology to access the information, field elements, and functionality required for completion and submission of the form, including all directions and cues.

The State of Pennsylvania's Initiative on Assistive Technology - PIAT provides WAVE which assesses websites by providing a linear reading of the site as if through reader software.

The National Cancer Institute (an element of the National Institutes of Health) has prepared and maintains a Federal-government related usability.gov website with considerable information relevant to other government and NASA.

This document was assembled to assist NASA and other Federal webmasters in the goal of making all Government websites accessible. Additional links and/or source material is invited. Please forward suggestions or corrections to Jayne Dutra, JPL, Co-chair, or Robin Land, LaRC, Co-Chair, NASA Webmasters, or Charles Redmond, NASA HQ Webmaster.